1. Field of the Invention
The invention relates to a procedure for producing coil-forming tubes, in which the tubes are heated to a temperature of 1,000-1,100.degree. C., particularly to 1,050.degree. C., and then bent at temperatures of more than 850.degree. C.
2. Description of the Prior Art
In wire mills, particularly high-performance wire mills, the wire product with the desired end diameter is formed into coils in the run-out area, and depending on the requirements is subjected to a further cooling while more or less spread out. In order to form the wire material, which is running in at high speed, into coils, coil-forming tubes are used, which are naturally subjected to relatively high levels of wear.
For the production of such coil-forming tubes, a procedure was hitherto chosen in which the tubes were heated for about 2 minutes at temperatures between 1,200.degree. and 1,250.degree. C. in the soaking zone of a furnace, after which a bending process was carried out in suitable bending devices. Since the tubes are supposed to be scale-free internally, the bent tubes were cleaned internally by means of sand-blasting. The replacement of tubes was carried out depending on wear, and a tube is usually changed when the remaining wall thickness is about 2 mm. The initial wall thickness of such coil-forming tubes is usually as much as 8 mm. With such known tubes, service lives of about 5,000 to 7,000 t [metric tons] of wire were achieved. Subsequently, this known procedure was optimized by limiting the temperature of the forming tubes before bending to a maximum of 1,050.degree. C., as a result of which it was possible to achieve an improvement in service life from 7,000 to about 15,000 t of wire.